Brush holders are known in the electric motor art. Typically comprising a pair of brush boxes for enabling a first and second brush joined with a first and second terminal wire to make contact with a commutator, prior holder designs provide support for the aforementioned electric motor components. During operation of an electric motor, current passes from the commutator through the brushes and terminal wires, and vice versa.
Several problems have arisen with regards to the known electric motor designs, and more specifically, known brush holder configurations. First, in assembling a brush holder, traditionally, each terminal wire is routed through the holder's support plate and then welded with its respective brush. However, by this arrangement, the durability of the brush-terminal wire joints have become an issue.
This first shortcoming may be best viewed in FIG. 1, where a brush terminal wire combination 10 is shown. Combination 10 comprises a cable 12 having an exposed wire 14. Moreover, combination 10 comprises a shunt 20, coupled with brush 22, which is crimped to an eyelet 21. Combination 10 is also attached to brush plate 31 by a rivet 17. Exposed wire 14 is joined to rivet 17 by way of a solder joint 18 to provide electrical contact between brush 22 and cable 12. While solder joint 18 electrically couples brush 22 with exposed wire 14, it also provides a poor means for physically securing both elements.
Furthermore, electric motors are also sources of electromagnetic interference ("EMI"). It is well known that EMI negatively affects the performance of electronic systems both proximate with an EMI source, as well as coupled to a power supply common with an EMI source. EMI is caused by the release of energy from an intermittent contact of brushes with the slotted outer surface of each commutator directly. As a result, EMI is transmitted through each terminal wire and radiated by the armature coils and the terminal wires. The electric motor, thus, acts essentially as an EMI source and transmitter.
In view of the above limitations, there presently exists a need for a brush holder which provides greater support and security for the connection electrically coupling the brush with the terminal wire. Moreover, a demand remains for a brush holder which provides for reduced EMI emissions.